Product Description:
FEATURES
Universal PCI, PCI-X, 3.3V and 5V compatible
Two, four, six, eight
and sixteen (respectively), 12-Bit, double-buffered, digital-to-analog
converters
Program
control provides means for either individual update or simultaneous
update of the DACs. The 8 and 16 channel models can use the counter-timer to generate DAC updates, and/or IRQs. The 2/4/6 models can use an external signal in this way.
Unique,
automatic control of DAC outputs to prevent spurious outputs
at power-on
24-bits (PCI-DA12-8/16) or 16-bits (PCI-DA12-2/4/6)
digital I/O buffered with tri-stateable transceivers
Three
16-bit Down counters (models PCI-DA12-8/16 only)
Resettable-fused
+5VDC available for external use
FUNCTIONAL
DESCRIPTION
PCI-DA12-8 and
PCI-DA12-16 are full-size cards that can be installed in long slots
of PCI-Bus computers. They contain eight and sixteen independent
double-buffered, digital-to-analog converters (DACs), and three 16-bit counter/timers. The PCI-DA12-2, -4, and -6 have two, four, and six DACs respectively. All of these cards have 8255 Compatible
digital input/outputs, 16bits are available on the PCI-DA12-2/4/6 models, and all 24 bits are available on the PCI-DA12-8/16 models. On the latter card a cable and bracket is provided to bring the 40-pin header signals to a 37-pin DB connector on an adjacent mounting bracket.
DIGITAL-TO-ANALOG
CONVERTERS
The DACs are
double-buffered and can be updated individually or simultaneously.
To assure that there will not be excessive outputs to external circuits
when the card is plugged in, automatic circuits limit analog outputs
to 15 percent of full scale when the card is powered up. Upon power-up,
the DAC reference voltage is set to that low voltage and the card
is set in the Simultaneous Update mode. Then, after values are loaded
into the DACs, you can use a software command to switch the DACs
to their respective full scale ranges.
Analog output
ranges available are:
- 0 to +2.5V
- 0 to +5V
- 0 to +10V
- -2.5 to
+2.5V
- -5 to +5V
- -10V to
+10V
- 4 mA to
20 mA
Higher drive current available on request
CALIBRATION
Calibration constants
are generated and stored in software using a program included with
the cards. ZERO (or OFFSET) constants are stored in EEPROM along
with SPAN calibration constants. Further, the EEPROM stores a table
of ranges that are assigned to each channel.
DIGITAL INPUT/OUTPUT
On the PCI-DA12-8 and PCI-DA12-16, a type 8255 Programmable
Peripheral (PPI) IC provides 24 bits of digital input/output. The
PPI is operated in Mode 0 and provides three 8-bit ports (A, B,
and C). Each port can be individually programmed for input or output.
Port C can be further configured as two 4-bit ports. Each digital
I/O line is buffered by a type LS245 tristate transceiver that can
source 15 mA and sink 24 mA (64 mA on request as a factory-installed
option). Pull-ups on the card assure that there are no erroneous
outputs at power-up and the buffers are configured for input or
output use by direction assignment from a control register in the
PPI. The PCI-DA12-2/4/6 cards use the same 8255 PPI, but bring only ports A and B to the connector, providing 16-bits of DI/O
COUNTER/TIMERS
Three 16-bit
down counters, in a type 8254 IC, are included on the PCI-DA12-8 and PCI-DA12-16. These are configured
as Event counters (See Block Diagram) and can also be used as a
frequency source derived from an on-board 1 MHz crystal-controlled
oscillator. These counters can generate IRQs at a programmed frequency, and/or initiate DAC updates. This allows for very precise timing of waveform generation.
INPUT/OUTPUT
CONNECTIONS
I/O connections
for the DACs are made at a 37-pin Sub-D Male connector on the card mounting
bracket. On the PCI-DA12-8/16 I/O connections for the digital inputs/outputs and the
counter/timers are made through a 40-pin insulation displacement
header and ribbon cable to a second bracket that can install alongside
the first. The PCI-DA12-2/4/6 models bring 16-bits of Digital I/O to the same 37-pin connector as the DAC data.
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